It's the Sunk Cost Fallacy. They have invested so deeply in this belief system that when presented with facts that dispute the very foundation of their echo chamber they can't even comprehend it. To change their minds would involve so much work and change all their friends and all their social media. Some of it is because they actually like what people like Trump and Putin do but some people actually have no idea how bad they are in the rabbit hole.

"the phenomenon whereby a person is reluctant to abandon a strategy or course of action because they have invested heavily in it, even when it is clear that abandonment would be more beneficial.

"the sunk-cost fallacy creeps into a lot of major financial decisions"